[PATCH 0/3] staging: sm750fb: Clean up helpers and fix DAC power-off handling

[PATCH 0/3] staging: sm750fb: Clean up helpers and fix DAC power-off handling

[Ali Köse]

This series replaces the set_DAC macro with a local static function,
corrects the DAC power-off bit handling, and removes an empty software
I2C acknowledgement helper and its ineffective parameter.

The first and third patches preserve existing behavior. The second
patch maps the extracted 0/1 DAC state to bit 20 rather than OR-ing it
into bit 0 of MISC_CTRL.

Based on staging-next at 6628e7d4c6b (Linux 7.4-rc1).

Validation:
- All SM750 driver objects compiled and linked into sm750fb.o with W=1,
  CONFIG_FB=y, CONFIG_STAGING=y, and CONFIG_FB_SM750=m.
- A standalone mocked-register test checked 72 DAC state and register
  preservation cases: 36 failed before the fix and none failed afterward.
- checkpatch.pl reported no errors or warnings.
- git diff --check passed.

Hardware testing was not performed.

Ali Köse (3):
  staging: sm750fb: Replace set_DAC macro with a static function
  staging: sm750fb: Fix DAC power-off bit handling
  staging: sm750fb: Remove empty software I2C acknowledgement helper

 drivers/staging/sm750fb/ddk750_display.c |  9 ++++++++-
 drivers/staging/sm750fb/ddk750_power.h   |  5 -----
 drivers/staging/sm750fb/ddk750_swi2c.c   | 19 ++-----------------
 3 files changed, 10 insertions(+), 23 deletions(-)


base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.53.0

[PATCH 1/3] staging: sm750fb: Replace set_DAC macro with a static function

[Ali Köse]

Replace the set_DAC macro with a static function named set_dac().
The helper has only one caller, so keep it local to ddk750_display.c
and remove the macro from ddk750_power.h.

This provides parameter type checking and follows kernel naming
conventions without changing the register operation.

Signed-off-by: Ali Köse <shroot1337@gmail.com>
---
 drivers/staging/sm750fb/ddk750_display.c | 8 +++++++-
 drivers/staging/sm750fb/ddk750_power.h   | 5 -----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/sm750fb/ddk750_display.c b/drivers/staging/sm750fb/ddk750_display.c
index 4e390541a507..d619e00fd88e 100644
--- a/drivers/staging/sm750fb/ddk750_display.c
+++ b/drivers/staging/sm750fb/ddk750_display.c
@@ -4,6 +4,12 @@
 #include "ddk750_display.h"
 #include "ddk750_power.h"
 
+static void set_dac(unsigned int off)
+{
+	poke32(MISC_CTRL,
+	       (peek32(MISC_CTRL) & ~MISC_CTRL_DAC_POWER_OFF) | off);
+}
+
 static void set_display_control(int ctrl, int disp_state)
 {
 	/* state != 0 means turn on both timing & plane en_bit */
@@ -151,7 +157,7 @@ void ddk750_set_logical_disp_out(enum disp_output output)
 	}
 
 	if (output & DAC_USAGE)
-		set_DAC((output & DAC_MASK) >> DAC_OFFSET);
+		set_dac((output & DAC_MASK) >> DAC_OFFSET);
 
 	if (output & DPMS_USAGE)
 		ddk750_set_dpms((output & DPMS_MASK) >> DPMS_OFFSET);
diff --git a/drivers/staging/sm750fb/ddk750_power.h b/drivers/staging/sm750fb/ddk750_power.h
index 0c4ab2120385..61f8608e59de 100644
--- a/drivers/staging/sm750fb/ddk750_power.h
+++ b/drivers/staging/sm750fb/ddk750_power.h
@@ -9,11 +9,6 @@ enum dpms {
 	CRT_DPMS_OFF = 0x3,
 };
 
-#define set_DAC(off) {							\
-	poke32(MISC_CTRL,						\
-	       (peek32(MISC_CTRL) & ~MISC_CTRL_DAC_POWER_OFF) | (off)); \
-}
-
 void ddk750_set_dpms(enum dpms state);
 void sm750_set_power_mode(unsigned int mode);
 void sm750_set_current_gate(unsigned int gate);
-- 
2.53.0

[PATCH 2/3] staging: sm750fb: Fix DAC power-off bit handling

[Ali Köse]

The DAC state extracted by ddk750_set_logical_disp_out() is either
0 or 1, but MISC_CTRL_DAC_POWER_OFF occupies bit 20. OR-ing the
extracted value directly into MISC_CTRL therefore clears the DAC
power-off bit and, when off is requested, sets bit 0 instead.

Translate the state into MISC_CTRL_DAC_POWER_OFF before updating
the register, preserving unrelated bits.

Fixes: 5372350be30a ("staging: sm750fb: use BIT macro for MISC_CTRL single-bit fields")
Signed-off-by: Ali Köse <shroot1337@gmail.com>
---
 drivers/staging/sm750fb/ddk750_display.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/sm750fb/ddk750_display.c b/drivers/staging/sm750fb/ddk750_display.c
index d619e00fd88e..dbbdbe08ad38 100644
--- a/drivers/staging/sm750fb/ddk750_display.c
+++ b/drivers/staging/sm750fb/ddk750_display.c
@@ -7,7 +7,8 @@
 static void set_dac(unsigned int off)
 {
 	poke32(MISC_CTRL,
-	       (peek32(MISC_CTRL) & ~MISC_CTRL_DAC_POWER_OFF) | off);
+	       (peek32(MISC_CTRL) & ~MISC_CTRL_DAC_POWER_OFF) |
+	       (off ? MISC_CTRL_DAC_POWER_OFF : 0));
 }
 
 static void set_display_control(int ctrl, int disp_state)
-- 
2.53.0

[PATCH 3/3] staging: sm750fb: Remove empty software I2C acknowledgement helper

[Ali Köse]

sw_i2c_ack() contains only a return statement, so calling it has
no effect. Remove the empty helper and the ack parameter from
sw_i2c_read_byte(), along with the parameter documentation.

Update the only caller to use the parameterless helper. The GPIO
operations and existing I2C bus behavior remain unchanged.

Signed-off-by: Ali Köse <shroot1337@gmail.com>
---
 drivers/staging/sm750fb/ddk750_swi2c.c | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/drivers/staging/sm750fb/ddk750_swi2c.c b/drivers/staging/sm750fb/ddk750_swi2c.c
index e63f3b00ec4c..54ce355e535f 100644
--- a/drivers/staging/sm750fb/ddk750_swi2c.c
+++ b/drivers/staging/sm750fb/ddk750_swi2c.c
@@ -201,14 +201,6 @@ static unsigned char sw_i2c_read_sda(void)
 		return 0;
 }
 
-/*
- *  This function sends ACK signal
- */
-static void sw_i2c_ack(void)
-{
-	return;  /* Single byte read is ok without it. */
-}
-
 /*
  *  This function sends the start command to the slave device
  */
@@ -300,14 +292,10 @@ static long sw_i2c_write_byte(unsigned char data)
 /*
  *  This function reads one byte from the slave device
  *
- *  Parameters:
- *      ack    - Flag to indicate either to send the acknowledge
- *            message to the slave device or not
- *
  *  Return Value:
  *      One byte data read from the Slave device
  */
-static unsigned char sw_i2c_read_byte(unsigned char ack)
+static unsigned char sw_i2c_read_byte(void)
 {
 	int i;
 	unsigned char data = 0;
@@ -326,9 +314,6 @@ static unsigned char sw_i2c_read_byte(unsigned char ack)
 		data |= (sw_i2c_read_sda() << i);
 	}
 
-	if (ack)
-		sw_i2c_ack();
-
 	/* Set the SCL Low and SDA High */
 	sw_i2c_scl(0);
 	sw_i2c_sda(1);
@@ -458,7 +443,7 @@ unsigned char sm750_sw_i2c_read_reg(unsigned char addr, unsigned char reg)
 	/* Get the bus again and get the data from the device read address */
 	sw_i2c_start();
 	sw_i2c_write_byte(addr + 1);
-	data = sw_i2c_read_byte(1);
+	data = sw_i2c_read_byte();
 
 	/* Stop swI2C and release the bus */
 	sw_i2c_stop();
-- 
2.53.0